tuning a tunnel ram intake

grumpyvette

Administrator
Staff member
I get asked to tune tunnel ram intakes fairly frequently,
and I think one reason, is many guys buy them with little or not much if any understanding of what that intake design was built to do,
but they like the "race LOOK" and want the "LOOK" and figure they can deal with the tuning issues, as they come up.
Id suggest you start by reading these linked threads,
keep in mind a tunnel ram intake is designed to run in the 3500 rpm-7000 plus rpm power band,
its an intake designed to maximize power and its generally not the best choice for a street car.
and that generally requires a cam with about a 240 @ .050 lift or greater duration, usually a reasonably tight 106-109 LSA,
open headers, at least 10.5:1 compression ratio,
and rear gears in the 3.73:1-4.56:1 range and a 3500 rpm stall speed or higher converter,
or a manual transmission to maximize the dual quad/tunnel ram intakes designed power curve potential.
yeah you can have a different basic combo, but the further you get from the design parameters,
the more difficult it becomes to tune and get it to run with a brisk crisp throttle responce, and no other issues.
and yes the larger the displacement , the higher the compression ratio, and closer the cam, duration,compression and exhaust header tune match
, the drive train gear ratios and the lighter the car is,
so the engine can maximize that intended upper rpm power band,
all the time the better that tunnel ram intake design, will tend to run.
many of the "problems" guys have running a tunnel ram intake have far less to do with the intake than the failure to operate it in its intended power band,
and match the other engine component selections to that power and rpm band for which it was designed.

https://pantera.infopop.cc/topic/individual-runner-carburetion

http://garage.grumpysperformance.co...-or-intake-is-too-restrictive.2994/#post-8394





    • https://www.summitracing.com/parts/hly-0-9377-1/overview/

    • IR refers to INDIVIDUAL RUNNER ,
      almost all tunnel rams are single plane intake designs with a small common plenum or two common plenums
      intake-tunnel.jpg
      tunnela3.jpg

      tunnela4.jpg


      edl7070.jpg



      IMG_1433.jpg
obviously if the intakes set up for use as a single runner intake tuning the cam timing, exhaust scavenging and displacement to the engines compression and gearing and throttle bore size is critical to making it function effectively in the intended rpm range
USE THE CALCULATORS
http://www.rbracing-rsr.com/runnertorquecalc.html
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php


80186-1_6.jpg


trmz.jpg


trmz15.jpg


yes there have been numerous attempts to use dominator carbs on IR intake designs
none have yet proven really successful as most designed intake and carb combos,
provide excellent torque but tend to lack enough air flow for impressive peak rpm
OFFY AND WEIAND both sold IR tunnel ram intake designs , that allowed a specific dominator carb, where each venturi was set up to have its own individual idle and jetting etc.
to be used as an individual runner carb design, but BOTH also sold bolt on common plenums to increase the intakes upper rpm flow and power potential.


irtl1.jpg

irtl2.jpg


irtl3.jpg

irtl4.jpg


http://garage.grumpysperformance.com/index.php?threads/dual-quads.444/

http://garage.grumpysperformance.com/index.php?threads/holley-accelerator-pumps-cams.1790/

http://garage.grumpysperformance.com/index.php?threads/holley-annular-vs-down-leg-boosters.5229/

http://garage.grumpysperformance.com/index.php?threads/carb-tuning-info-and-links.109/

http://garage.grumpysperformance.com/index.php?threads/setting-up-your-fuel-system.211/

http://garage.grumpysperformance.com/index.php?threads/holley-carb-power-valves.1639/

http://garage.grumpysperformance.co...cedure-step-by-step-guide-with-pictures.5378/

http://garage.grumpysperformance.com/index.php?threads/is-backpressure-hurting-your-combo.495/
keep in mind that just about anything you can do to make it easier to efficiently fill the engines cylinders will tend to increase efficiency and as a result power, the basic tunnel-ram style intake provides a very effective way to allow the fuel/air mix to enter the cylinder head ports with less flow restriction than most other intake manifold designs.
but theres almost always ways to reduce flow restriction and increase efficiency, most tunnel ram intakes are mass produced castings that will benefit from some careful port and runner clean-up work.
port matching would be an obvious first step, but plenum and runner mods can and usually do help power produced.
PORTING THE TUNNEL RAM INTAKE RUNNERS CAN AT TIMES PROVIDE VERY NOTICEABLE GAINS
keep in mind engine displacement, cam timing, compression ratio all effect the intake flow but its generally a taking the time and effort to match the cam timing , overlap and designed rpm range and well matched header and tuning the exhaust scavenging that will have the most noticeable effect and potential improvement on a tunnel rams flow characteristics

oldnewholleystealthram.JPG

hsrrunners.jpg

stock un-ported runner entrances of a stealth-ram intake base above


the same intake manifold design, lower runner entrance's after some runner entrance port work.

portedhsr.jpg

porting helps flow significantly

A properly set up and correctly tuned tunnel ram intake is designed to maximize an engines power band in the 5000-rpm-7500-rpm range on most v8 muscle car engines, its never going to be ideal cruising at below 5000-rpm but that does not mean it can't be used or that its going to be useless on a street driven muscle car, provided the owner knows how to adjust and tune it.
AND I'M ALMOST ALWAYS AMAZED AT THE COMPLETE MIS-MATCH OF PARTS, MOST GUYS ASSEMBLE THAT THEY THEN EXPECT TO RUN CORRECTLY.
and as usual, a bit of careful research into matching engine compression,
cylinder head, port cross sectional area,
runner length, cam timing, cam LSA,valve lift and duration,
head flow potential,collector length,
and exhaust header design,in general to inhance scavenging,
the cars gearing, carburator ,fuel/air ratio,fuel atomization, ignition advance curve,tire diameter, drive train gearing,etc.
to match the intended power band will go a long way towards getting any tuunnel ram intake to perform well

the most important and effective performance asset you have is simply your ability to ask yourself questions, the ability to think logically isolate and test components carefully and doing the research if its required to find the best answer's you'll need.

A well designed tunnel ram intake, with matching carburetors provides about the most direct, efficient ,strait line,path for the fuel/air mix, from carb to cylinder possible,only some of the individual runner stack injection intakes provide a more robust torque curve in the mid and upper rpm ranges, and once the engine operating rpm range or engine speed, cam timing and engine displacement, and exhaust scavenging components are well matched in an application, you can generally make exceptional power levels, but keep in mind the basic design requires you to get up into the 250-300 fps range for air flow inertia to become highly effective filling the cylinders.
the first issue most guys need to understand is that in most cases, both carbs will need to be jetted the same on all four corners and the opening synchronized so the fuel air mix is consistent before during and after the transition from idle to wide open throttle, and that your idle speed and quality of the idle will be dependent on your being able to read the plugs and determine whats going on in the combustion chamber.(this is rarely good for mileage or how the engine will run below about 4000rpm, but then the intake was and is designed primarily for operation above 4000rpm with little or no concern for its power curve or efficiency below that rpm level.
now I,m not suggesting a good tuner can,t make the car run reasonably well with a tunnel ram intake on the street,but its never going to be the ideal intake design on an engine loafing along below 3500rpm, 90% of the time ,especially if good throttle response and mileage are a primary goal. I can tell you from experience that the larger the displacement engines tend to be more tolerant of street use off that tunnel ram intake design, and gearing and cam timing and efficient header scavenging is critical to getting good results.
if the engine won,t idle you most likely have a vacuum leak or some fuel/air ratio issues or the timings off.
Yes you can tune a tunnel ram intake to make both good power and torque, in fact if the parts are correctly matched power from about 3500rpm-8000rpm will match or exceed most other choices, and a good tuner familiar with tuning a tunnel ram should be able to get the combo to run without a stumble or flat spots in the power curve.. because a tunnel ram intake by design has a strait shot at the back of the intake valve in the cylinder heads from the plenum with the least restriction to flow possible these intakes tend to make excellent upper mid rpm and peak power.
One factor thats frequently over looked is that most tunnel ram dual quad intakes have nearly identical runner dimensions and an almost direct strait line path from the carburetor s venturi to the back of the intake valve on each cylinder, (unlike most dual and single plane single carb intakes) which can easily be worth an extra 1%-3% in power due to reduced flow restriction
I,ve frequently seen a 4%-8% % power gain from a properly tuned, dual quad tunnel ram intake over the best I could get from the single carb intake manifold designs, due to both the reduced flow restriction and better fuel/air ratio control between cylinders, but remember most tunnel ram intakes won,t produce those benefits until they operate in the designed rpm range which frequently starts at or above 4000rpm
portmatchtunnel.jpg

keep in mind many EFI intakes are updated versions if the basic tunnel-ram intake design offering superior dry air flow and a direct injector shot of a high pressure mist of fuel aimed at the back of the intake valve
efitram.jpg


tramp3.JPG

obviously you will need to carefully port match some intakes to some head ports due to the wide variation in sizes and shapes
PortMatch02.jpg

PortMatch03.jpg

PORT MATCHING THE INTAKE RUNNER EXIT TO THE CYLINDER HEAD PORT ENTRANCE USUALLY HELPS REDUCE RESTRICTIONS TO FLOW RATES, AND REDUCES FUEL/AIR DISTRIBUTION ISSUES

thats very useful info,
http://airdensityonline.com/free-calcs/
many guys fail to realize that only about 21% of the air content is oxygen thats physically useful in converting the fuels potential energy content into heat,
and rapidly expanding gases that produce the cylinder pressure that drives the piston down the cylinder, maintaining the ideal fuel to oxygen ratio will vary with altitude.
as a result the cost to run the car goes up and the cars power can go down.
another factor ignored is that not only does less dense air contain less oxygen it holds less MASS thus the inertia of the exhaust gasses exiting the headers has a bit less scavenging effect on the next incoming charge in the intake runner following it during overlap in cam timing
Stoich.gif

volumetric.gif

exhaustpressure.jpg

pistonposition2a.jpg

EXFLOWZ4.jpg

AFR_Torque.gif

Fuel-Pump-Flow-Requirements.jpg



YOU MIGHT WANT TO ALSO READ THESE THREADS



http://garage.grumpysperformance.com/index.php?threads/options-on-dual-quads.11047/

http://garage.grumpysperformance.co...ical-constant-flow-injection.4502/#post-49562



http://www.superchevy.com/how-to/engines-drivetrain/sucp-0612-big-block-tunnel-ram-intake/

https://www.profilerperformance.com/216-bbc-tunnel-ram.html

http://www.jegs.com/p/Dart/Dart-Big-Block-Chevy-Tunnel-Ram-Intake-Manifolds/957642/10002/-1

summit racing has some package deals
http://www.summitracing.com/parts/sum-cwnd304





http://www.force-efi.com/machefi.htm

http://www.international-auto.com/fiat- ... gauges.cfm



http://mysite.verizon.net/vzezeqah/site ... ystems.pdf



yes you can run a tunnel ram intake with a small cam and small carburetors on the street, just for looks, yes they do make street tunnel rams with smaller runners that are designed to operate at lower rpms that the real race tunnel ram intake designs,and in that type of application you can set the carburetors to work progressively, but it won,t run ideally, youll loose a good deal of low and mid rpm torque and you'll never get near the benefits of the intake design, but yeah, it can be assembled and tuned to function, if your just into (THE LOOK)

lets go over the basics, most tunnel ram intakes are designed to operate efficiently in the 4000 rpm-8000 rpm power band, with TWO MATCHED 4 BARREL carburetors, they are race intake designs meant to maximize flow and minimize and port flow restrictions, and basically designed to be operated at wide open throttle most of the time, and use dual 4 barrel carburetors, so each carburetors venturie is effectively dropping its fuel/air mix into its own designated intake port, this mandates all four venturie,s should be jetted very similar and that the throttle blades on all four venturie,s in the carburetors open at approximately the same rate,and having two carburetors feed a single intake effectively reduces the vacuum signal each carburetors sees
,so power valves and jetting and accelerator pumps must compensate, that higher intended power band by default means that the engine must also have a cam with matching duration and LSA and heads designed to flow a fuel/air mix in the same basic power band,that will open the valves long enough and far enough to maximize the intake runner flow rates at that intended upper rpm power band, in most cases thats going to be somewhat dependent on engine displacement and compression but a good rule of thumb is a minimum of 10.5:1-13.5:1 compression and a cam with a 245-300 duration @ .050 lift to match the duration and resulting dynamic compression
to get a good even controllable fuel air ratio entering into each port , you ideally have two matched carburetors with 8 throttle bores located over the intake runner entrances with the jets flowing enough fuel to supply abut the ideal 12.6-13.0:1 fuel air ratio in that intended power band and intake runner cross sectional areas matched to the engines displacement and power band.
so you can,t just throw on two old quadra-jet carburetors, or vacuum secondary Holley,s and expect it to run correctly, now IM not saying it can run reasonably well if your skilled at tuning ,but it certainly will never reach its full potential with the mis-matched components.
if your setting the intake up to provide its maximum power potential the throttle linkage should open all the venturies at the same rate , and youll rarely be running the engine under 4000rpm, from the launch to the mph lights at the end of the strip
keep in mind a tunnel ram intake is designed to have an open carburetor venturie almost directly over each runner feeding that cylinder, and in most cases a small plenum to allow some small cross over so each intake runner has access to slightly more fuel/air mix than the single carb venturie supplying it alone can easily supply, theres usually a direct strait line shot from the back of the intake valve up thru the carb venturie, but the ideal flow requires high air and port speeds so the system works best well above about 4500rpm in most applications, and only if all 8 venturies flow equally, this is best accomplished when all eight venturies open equally and jetting, fuel pressure and accessories like power valves and boosters are consistent, because, maintaining equal fuel/air ratios, ie, fuel droplets or mist suspended in the air flow does not like rapid changes in direction of flow
0210hpp_flow04.jpg

I generally start with 7.5 power valves and #82 jets on all locations a 5.5 psi of fuel pressure then move up or down in jets or power valves as required, youll find it best to buy jets in these multi packs then re-place what you use

http://www.summitracing.com/parts/HLY-36-181/
hly-36-181.jpg

tunnela1.jpg

tunnela2.jpg

tunnela3.jpg

tunnela4.jpg


BEFORE PORT/RUNNER CLEAN UP>>>>>>>>>>>>>>>>>>>>>>>>>>>>AFTER PORT/RUNNER CLEAN UP AND PORTING


two 450cfm Holley work reasonably well on a street car
http://www.summitracing.com/parts/CMB-03-0177/

two 600cfm Holley work reasonably well on a street/strip car
http://www.summitracing.com/parts/CMB-03-0183/?rtype=10

portmatchtunnel.jpg

one reason a properly port matched tunnel ram intake flows efficiently is a strait path to the intake valve, in the cylinder head from the plenum

http://www.allcarbs.com/detail.php?pid= ... n=71&stt=0

two 1050 Holley dominators work reasonably well on a big block strip car
http://www.holley.com/0-9375-1.asp
http://www.profilerperformance.com/tunn ... v-216.html

edl7070.jpg



IMG_1433.jpg

SCP27.JPG

dualedlprogressive2.jpg

003-2-1.jpg

LSAChart01.jpg



Duration_v_RPM-Range_wIntakeManifold01.jpg


calculate port size
http://www.wallaceracing.com/runnertorquecalc.php

http://www.wallaceracing.com/lpv.php

http://www.73-87.com/7387garage/drivetrain/hei.htm

http://www.swartzracingmanifolds.com/tech/index.htm



t-ram.jpg


p128621_image_large.jpg


RELATED INFO

http://www.hotrod.com/techarticles/carb ... index.html






INTERESTING RELATE ARTICLEs

http://www.superchevy.com/technical/eng ... index.html

http://www.carcraft.com/techarticles/03 ... index.html


holley20-28.jpg

http://www.holley.com/20-28.asp
http://www.holley.com/data/Products/Tec ... 9R8291.pdf
if your using two holley vacuum secondary carbs on the street.....this might prove useful
to try to maintain exactly even fuel distribution between runners...which will almost never happen if the carbs open in a totally non synchronized manor


BTW contact the cam manufacturer, as theres a thousand or more valid combos
but two cams Ive had very good results with recently when using the tunnel ram intake, design, are these,crane cams listed below, both were used in reasonably light weight cars with manual transmissions and cars with at least 11:1 cpr and 3.90:1-4.11"1 rear gearing, one was a 383,sbc the other was a 496bbc, youll obviously need to match tire diam. and gearing to match the engines power curve and keep the rpms in top gear reasonable as the car runs thru the lights at the end of the track.


bbc http://www.cranecams.com/product/cart.p ... il&p=24613

sbc http://www.cranecams.com/product/cart.p ... il&p=24572
 
Last edited by a moderator:
I was recently re-reading a magazine article where they compared the results they got on a fairly well designed 383 sbc, from a dual plane , a single plane and a tunnel ram intake induction system,they tested several intakes two different cylinder heads and two different cams, all in all it was a very good article, but it failed to point out that the three different intake designs are best used on three totally different engine combos, now both the single carburetor intakes used the same 750cfm carburetor and the tunnel ram used two 600 cfm carburetors, and I do fully understand that if they changed a bunch of parts they would effectively be testing three or more totally different engines making much of the comparison rather useless., but the engine had both heads and a cam almost perfectly matched to the cam the dual plane intake would match best, thus the single plane did not provide decent hp numbers until both the larger heads and larger cam allowed it to reach more of its flow potential. and the tunnel ram was treated as an after thought,while they freely admitted, that on a street car, two 450cfm carburetors would more than likely provided a crisper response and more torque.
they also admitted not taking the time to really sort out the dual carburetor s or tune the car while it had the tunnel ram intake installed and acted surprised that the tunnel ram made less mid rpm power than either of the single carburetor intakes.
now if your not going to take the time to maximize the intakes potential its hardly surprising that it will not produce to its full potential.
most tunnel ram intakes are a RACE ONLY max effort design made to maximize power in the 5000rpm-7600rpm- and up rpm range so its hardly fair to fault the intake if its used at lower rpms or if its matched to components meant to run at lower rpms.
thats kind of like taking an Olympic distance runner and asking him to compete in weight lifting.

it generally helps to have a few diagnostic tools at hand, they don,t need to be top quality but you do benefit from experience and the knowledge of what your trying to accomplish and an isolate and test mentality







Id strongly suggest you read these threads also
http://garage.grumpysperformance.com/index.php?threads/setting-up-your-fuel-system.211/

http://garage.grumpysperformance.com/index.php?threads/fuel-pressure-regulators.635/

http://garage.grumpysperformance.com/index.php?threads/how-big-a-fuel-pump-do-you-need.1939/

http://garage.grumpysperformance.com/index.php?threads/dual-quads.444/



intake-tunnel.jpg


efit1.jpg

Ive tuned a good many cars with tunnel ram intakes and when properly set up they do produce better PEAK power levels,and can be made to run decently on a street car application, but they were never designed for off idle rpms or driving in traffic, if you don,t spend 70% of your time with your throttle wide open and your foot on the floor the tunnel ram intake may not be the best choice.
when tuning a tunnel ram you start by jetting all 8 jets equally and generally use a longer accelerator pump shot duration and a higher numerical power valve than a similar single carburetor might. if the carb allows swapping booster,annular boosters usually generate a higher vacuum signal strength from increased air velocity due to their being more restrictive than the down leg boosters, in an identical throttle bore size, allowing the use of larger carburetors and/or larger cams while still retaining good metering stability. This higher signal strength however sometimes requires smaller jetting than an otherwise identical down leg booster carburetor, and your generally not going to get ideal mileage from a properly tuned tunnel ram, as its designed exclusively for max power potential .
yes a tunnel ram may look really cool, yes its very possible to get it to run fairly decent on a street car, but its not likely to be nearly as responsive at low rpms as a good dual plane intake on most street cars, and a tunnel rams not going to run ideally if its set up to progressively open each of the 4 sets of dual carburetor venturies. a tunnel rams designed to feed each runner from the carbs port or venturie located roughly above it so theres a strait line of air flowing from the carburetor venturie to the back of the intake valve in the cylinder head below it, if you disrupt the plenum flow by constantly changing the source of the air/fuel mix into the plenum the intake runners tend to get far from ideal fuel/air distribution, during much of the constantly changing distribution of air flow into the plenum.obviously knowing how to read plugs correctly, having a vacuum gauge, fuel pressure gauge and timing light and a marked damper are mandatory


BTW, in some applications adding a carefully cut and placed screen, under the carburetor spacer can be added too catch debris that might fall into the carburetor,and save you a good deal of engine damage ,(If my experience and those of several friends is what many of you can expect, keep in mind youll occasionally be forced too deal with deliberate sabotage, where morons drop crap into the carburetor's if the car is left UN-attended and easily accessed in some areas) I don,t know why dual carburetor tunnel ram intakes tend to attract morons but Ive seen this on several cars at car shows adding the screens has the potential added benefit that the screen tends to increase fuel air atomization, by breaking up fuel droplets as they enter the plenum, area of the intake, a screen with 1/8" holes has only a minor effect on air flow rates
carbscreena.jpg

afrchart

RELATED INFO youll be tending to skip that youll regret later if you do.

http://www.chevydiy.com/chevy-big-block-performance-tunnel-ram-intake-manifolds/


http://www.carcraft.com/techarticles/se ... index.html

http://garage.grumpysperformance.com/index.php?threads/stumble-on-launch.15477/


keep in mind that exhaust scavenging has a huge effect on intake manifold flow & efficiency
http://garage.grumpysperformance.com/index.php?threads/is-backpressure-hurting-your-combo.495/
 
Last edited by a moderator:
one factor you want to keep firmly in mind is that a tunnel ram, is designed for the upper rpm range and REQUIRES high air flow speeds in the runners to maintain a fairly consistent fuel/air ratio in each intake port, this is NOT, something that you can generally maintain unless all 8 carburetor venturies open at exactly the same rate and usually requires equal or nearly equal jet sizes, in an ideal set-up each carburetor venturies roughly centered over an intake runner and the majority of the fuel/air mix drops in a direct strait line from the carburetors individual throttle bore strait to the back of the intake valve in its matched runner, the plenum acts like a reversion buffer and adds extra air flow potential but if theres not almost a direct strait line from the carburetor to the intake valve in the intake runner below it the design is usually subject to fuel/air ratio variations that tend to hurt power.
One other factor is that the intake runners cross sectional area should be no smaller and not much larger than the cylinder heads used, and the cam must have the duration and lift to allow the port to flow to the cylinder heads full potential.this is frequently a miss matched factor
example
lets say your building a 454 big block and your looking at two different tunnel ram intakes , after careful measurement you find your intake valve is 2.19" and has about a 3.45 square inch valve throat area, and that will require a cam with at least a .600 lift and at least a 245 duration to come close to allowing the port to flow to its full potential,the intakes designed to operate above 4500rpm, so you want an intake runner having at least the 3.45 square inch area, anything smaller won,t allow the tunnel ram intake to reach its full flow rate, but anything much larger will just lower port speeds and mid and upper rpm responsiveness to some extent
piston speeds are limited to about 4000fpm-4500fpm, on a 454 with its 4" stroke thats generally going to limit you to about 6800rpm as a absolute safe max if DEPENDABILITY is a long term concern as piston speeds much higher induce considerable increased stress.
A bit of MATH will tell you that a 454 spinning 6800rpm will require about 900-1100cfm flow from the TWO combined carbs,, so in theory two 500cfm-650cfm carbs would be enough but in the real world the reduced vacuum under the carbs effects the flow rates significantly (keep in mind the LOWER flow rate at the reduced vacuum, in the plenum, due to 8 carburetor venturies feeding a single plenum, thus a carb rated at 600cfm used in a dual carburetor config will commonly flow a bit less due to the lower vacuum under the venturies
and yes, use of a small handy and accurate fuel pressure gauge, mounted on the fuel injector fuel rail (0-100 psi for FUEL INJECTION)
fpgg3a.jpg

or carb inlet port (0-15 psi for carburetors)is almost mandatory, they generally cost under $30
fpgg1a.jpg
fpgg2a.jpg

555-BO-1672-wGa.jpg

viewtopic.php?f=55&t=5229


A VERY USEFUL set of CALCULATORs

http://users.erols.com/srweiss/calcdchg.htm
a carb flows less if the plenum vacuum is less

http://www.rbracing-rsr.com/runnertorquecalc.html

http://www.wallaceracing.com/runnertorquecalc.php

http://www.wallaceracing.com/lpv.php

http://users.erols.com/srweiss/calccsa.htm

http://users.erols.com/srweiss/calcplv.htm

http://users.erols.com/srweiss/calcfps.htm

http://users.erols.com/srweiss/calcacsa.htm
on the better 23 degree SMALL BLOCK AFTERMARKET HEADS THERE'S ABOUT 5.5 INCHES OF INTAKE PORT LENGTH ON AVERAGE FROM INTAKE GASKET TO THE BACK OF THE INTAKE VALVE AT THE FAR EDGE
P12CHARTS.jpg

curtainareaonvalve.jpg

Duration_v_RPM-Range_wIntakeManifold01.jpg

vechart.gif

runnerlength2.jpg

Wave%20Pulse%20RPM%20Chart.jpg

intake runner stack length changes, and to some extent cam timing can be used to tune the torque peaks
SCP27.JPG

dualedlprogressive2.jpg

RELATED INFO youll really need




OFFY CROSS RAM BELOW
yes they are still available new, yes they work rather well once the engines above about 3500rpm if properly set up and tuned
and Ive used them in several engine combos

ofy11.jpg

ofy22.jpg

manifoldmu1.jpg


manifoldcarbsrt0.jpg


AND YES CHEVY AND EDELBROCK USED TO SELL VERY SIMILAR CROSS RAM INTAKES
xram2.gif


BTW heres the cam I usually use with a CROSS RAM APPLICATION
http://www.cranecams.com/product/cart.p ... il&p=23968
the cross ram intake REQUIRES an engine with about 11:1-12:1 compression,good headers with a low restriction exhaust, a manual transmission and 3.90:1-4.56:1 rear gears to work correctly, Ive used them mostly on 377 and 406 and 383 displacements with two identical 600cfm carbs, but I know other success full cases using two 450 cfm carbs , just be aware this intakes designed to run in the 3500rpm-7000rpm power band all the time, on a engine with open or low restriction exhaust and a solid lifter or roller cam and heads that flow a minimum of about 250cfm at .500 lift
The Engineering Truth..
even back in the early 1960s they were well aware that long intake runners on race engines provided a significant inertial ram tuning benefit that increased mid range torque
ramtunein.jpg

The Cross Ram was never intended, nor was it developed (tuned) to be used with the Smog Equipment. The only reason it appeared in the Car Life article (and others) was to satisfy the Corporate mandate to pre-empt any negative connotations derived from the article that might imply Chevrolet was not in sync, or worse yet, ran counter to the Government mandated SMOG laws. It was a risk that Chevrolet could not afford to take for political reasons.

The true intent by Chevrolet was to have the tuner build the Cross Ram equipped 302 in the "recommended" tuned state it was developed for using Chevrolets Tubular Headers with specific timing and tuning considerations - never with the Smog Pump since it was counter indicated for performance which was implied and understood by all race tuners and street racers back in the day.

PERFORMANCE FACTS:

The SMOG Pump is actually a centrifugal AIR pump that forces compressed air into the exhaust manifolds to decrease the hydrocarbons by DILUTION. A totally ineffective smog reducer and supreme power waster that adds extra weight. In fact, you could make the argument that it actually increases pollution due to its inefficiency. No one was fooled by it back in the day.

The Smog Pump will cost you 15 important hp in the lower rpm ranges that you will not want to lose
Use of the equipment prohibits optimum jetting and timing and therefore;
The optimum power/torque distribution curve is not achievable and at best you will end up with a de-tuned 302

Bottom Line - The only reason the 302 appeared in some publications with the Smog Equipment was to appease Corporate Management and placate the Government. Understanding that, if you go with-out the pump as intended, you will benefit from maximum power which is consistent with Chevrolets true intent for the Cross Ram and from a pure nostalgic point of view be in sync with what everyone actually did back in the day. That is the true spirit of the Cross Ram equipped 302.

YES READ THE LINKED INFO ITS WORTH THE EFFORT

http://www.vintagemusclecarparts.com/pa ... sram1.html

http://guinns-engineering.com/Cross Ram FAQ's.htm

http://www.superchevy.com/technical/eng ... index.html

http://www.carcraft.com/techarticles/03 ... index.html

obviously theres a wide variation in quality and most modern cars with EFI use oxygen sensors used in the exhaust of cars to do this type of sensor work and NOTHING ELECTRONIC in nature lasts forever,but the sensors are used to feed constant data on remaining un-burnt oxygen in the exhaust back to the computer controlling the fuel injector pulse duration,yes in some cases its potentially possible to damage the sensors, sensors normally last 3-6 years in service, but in most cases its not critical if properly installed , and not all that expensive or time consuming to replace them on occasion,so its not a big deal to suggest a dash mounted fuel/air ratio gauge be used as a tuning tool on a carburetor equipped engine, there even several BUILD IT YOURSELF F/A RATIO GAUGES

http://www.scirocco.org/tech/misc/afgauge/af.html

http://www.aces.edu/~parmega/efi/temp/wb/guide.html

http://www.autospeed.com.au/cms/A_1716/ ... larArticle

http://www.autospeed.com.au/cms/A_0217/ ... larArticle

http://www.davessmallbodyheis.com/

http://www.jaycar.com.au/productView.as ... BCATID=347

http://www.eagle-research.com/cms/store ... cer-manual

http://www.youtube.com/watch?v=sS6olf1o ... ure=fvwrel

http://www.youtube.com/watch?v=RizrDvP8 ... re=related
 
Last edited by a moderator:
intake-tunnel.jpg

BTW ONE TUNING TRICK used for decades is to install a divide wall made of perforated aluminum to separate the two sides of the tunnel ram plenum as it tends to increase throttle response , and reduce tuning issues, because having it installed greatly reduces the tendency to un-equal fuel distribution , remember the firing order 1,8,4,3,6,5,7,2....without the divider wall , 2 tends to steal #1s intake charge just as #4 does from #3 and #6 does from #5, because the follow each other in the firing order and the intake runner entrances are located next to each other in the plenum
with the divider in place there is frequently a noticeable change in many cases in how the plugs look and how the engine runs so its worth it to test in your engine combo, welding in the perforated sheet, plenum divider wall, , is not mandatory but Ii have seen it work rather well in several engines
BTW just some info
the reason that tunnel ram intake was designed like that was that back when the holley dominator carburetors first came out , it was felt that a tunnel ram that allowed the carb to be bolted to the intake so that each carb throttle body venturie should feed each individual runner separately, that's why the lower intake plenum bolt spacing, matches the dominator bolt mount spacing, this in theory provides an individual runner intakes tunning advantages but the holley dominator throttle bore diameter is not large enough in cross sectional area to provide adequate flow rates for much over a 383 engine displacement in that config so a spacer plenum was quickly added to allow multiple throttle bores to supply each intake runner port entrance.
obviously the dominator carb model with the individually adjustable 4 corner idle screws was required, and theres 750 cfm,1050 cfm , 1150 cfm and 1250 cfm versions of the dominator carbs, and a direct 1:1 secondary throttle blade linkage kit that made each throttle open simultaneously was required
80186-1_5.jpg
http://m.summitracing.com/search?keyword=dominator carburetor models

http://m.summitracing.com/search?keyword=dominator carburetor models&page=2

http://m.summitracing.com/search?keyword=dominator carburetor models&page=3

https://www.holley.com/products/fuel_systems/carburetor_components/brackets_and_linkage/parts/20-5

obviously if the intakes set up for use as a single runner intake tuning the cam timing, exhaust scavenging and displacement to the engines compression and gearing and throttle bore size is critical to making it function effectively in the intended rpm range
USE THE CALCULATORS
http://www.rbracing-rsr.com/runnertorquecalc.html
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php


80186-1_6.jpg


trmz.jpg

carefully done, port work on the intake runners and plenum can produce significant flow rate improvements
fordman1&2.jpg

trmz15.jpg


v8-firing-flowchart.png

MTCooksoon.jpg




perforatedx.jpg

intakew-tunnel.jpg

SCP27.JPG

TunnelRamWithPeforatedDivider02.jpg

few guys realize that many successful racers don,t use tunnel ram intakes in exactly the same condition they came out of the box in, theres tweaks that improve results
welding in a center baffle of perforated aluminum sheet helps increase throttle response and equalize fuel/air ratios between cylinders in many applications

if you look at the plenum youll see that a center baffle prevents most of side by side runner entrances from stealing charge flow from each other by preventing two successive intake ports from drawing from the plenum in the exact same area in rapid succession, a welded in baffle leaves only the 5-7 cylinder stealing charge , while without the baffle the 1-2, 5-7,3-4, 5-6 all have runner entrances pull charge from the plenum in rapid succession,from adjacent runner entrances use of the center baffle is not a huge benefit in all cases, but in SOME applications you see some gains
MTCooksoonfdvb.jpg
 
Last edited by a moderator:
The amount of free flow area would be a tuning device. One could weld in
some U Channel and the vertical sides so that you could slip in different
perforated metal dividers with different hole sizes.




 

Attachments

  • AluminumChannel.jpg
    AluminumChannel.jpg
    8.2 KB · Views: 792
the ability to weld in a 3 sided aluminum u-channel so you can easily drop in, and test,and easily exchange different plenum divider walls with a different percentage of open surface areas,is yet, another good idea!,

aluminumchannel.jpg
 
http://www.carcraft.com/techarticles/03 ... index.html

Car Craft, February, 2009
Email

What's the ultimate naturally aspirated intake-manifold design? Is it a modern single-plane or a tunnel-ram? That's a question we intend to answer with this dyno-test.

The PlayersTunnel-ram intake manifolds made their first known dragstrip appearance on the legendary Ram Chargers "High and Mighty" '49 Plymouth in 1959. A group of hobbyists consisting largely of Chrysler engineers, the Ram Chargers created a new style of manifold by mounting a pair of Carter AFB carburetors over a common plenum and runners made from industrial-grade rubber hose. Thus the first tunnel-ram was born, attached to a 354-inch Hemi. Popular in the '60s and '70s with car crafters, the tunnel-ram enjoyed quite a following until the advent of modern, technologically advanced single four-barrel intakes that offered easier packaging and the simplicity of tuning one carburetor.

In racing classes with no limitations on carburetion, tunnel-rams live on in high-tech sheetmetal and carbon-fiber form. In the ultimate expression of normally aspirated performance, NHRA Pro Stockers are exclusively equipped with tunnel-ram-style induction. But, like most performance components, tunnel-rams are combination specific; we don't recommend slapping one on a 300-inch 8:1 compression engine.

According to Air Flow Research's Tony Mamo, a tunnel-ram-equipped engine should flow more air than one with a conventional single four-barrel intake manifold because it fools the motor into thinking it has better heads-even if the heads are very good. If, on a flowbench, a single four-barrel intake manifold is substituted for a radius plate (normally being attached to the port being tested), it is not uncommon to see significant decreases in flow because of the turn in the runner inherent to a single-plane design.

Our test vehicle was equipped with a Mopar Performance tunnel-ram for W-2 cylinder heads. Unlike its predecessors from the '70s, this modern design is a race unit with relatively short runners. The carburetion perched atop the intake consists of a pair of Holley 650 mechanical secondary double-pumpers equipped with Proform carb bodies. The Proform bodies feature no choke horns, nicely sculpted air entries, down-leg boosters, and screw-in air bleeds. It appeared somewhat cobbled together, but the dyno indicated that the carbs were working pretty well, especially after we got the air/fuel ratio dialed in with the high-speed air bleeds.

To pit the venerable tunnel-ram against a contemporary single-plane design, we had to locate an intake with a large plenum volume. Representing modern single-plane technology is a relative newcomer in the realm of small-block Mopar single-plane intakes. Designed and manufactured by Indy Cylinder Heads, the Indy 360-3 was designed for use with the company's own aluminum small-block cylinder heads, which are similar to the venerable W-2. The W-2, born out of the Pro Stock wars in 1976, is an iron, open-chamber design with oval intake ports featuring relocated pushrod holes that necessitate offset rocker arms. Though designed over two decades ago, they still prove formidable.

The manifold is a direct bolt-on for standard W-2 heads, featuring beautifully shaped runners with consistent port volume and a very large plenum. The high-rise Indy intake promised to give the mighty ram a run for its money, topped with an equally serious Holley 950 HP carburetor. Also a mechanical-secondary double-pumper design, the 950 HP comes with all the features a custom carb shop would equip a race carb with, including screw-in air bleeds, a milled-off choke tower, double-step down-leg boosters, and improved metering circuits. Both intakes represent state-of-the-art technology, and if any single-plane can be a contender in this arena, this is the one.

The TestOne week prior to our showdown, we spent an entire day working the bugs out of our tunnel-ram carburetor combination on Westech's SuperFlow chassis dyno. What we ended up with was a seriously stout small-block posting an output of 532 hp at the rear wheels.

After a thorough engine cooldown, we got to work swapping intakes. Having grown accustomed to the look of the tunnel-ram, a single four-barrel just seemed modest by comparison. Once bolted down, the Holley 950 was mounted, the linkage was connected and adjusted, and the beast was fired. We adjusted the idle and made our first partial pull to determine how far off the fuel mixture was. It looked good enough to pull all the way to 7,000 rpm. The air/fuel ratios were right on the money. No tweaking, no tuning, no jetting, no nothing. Out of the box, the Holley proved lethal. We cooled the Barracuda down and pulled it to 7,300 rpm. We were rewarded with just under 513 hp at the rear wheels. This Indy/Holley combination was proving very effective. We performed a backup pull to make sure the 513 horses weren't a fluke and were handed another 513 hp ticket. No controversy here.

What We learnedWell-designed tunnel-rams work. They make big torque and horsepower everywhere and carry the torque a great distance. You will notice by the dyno charts that the ram produced prodigious amounts of torque and horsepower well past 7,000 rpm, while the single-plane dropped off rather rapidly past its peak of 7,000 rpm. The ram usefully extends the powerband of the engine, enabling you to run a numerically higher gear than you would be able to with a single four-barrel induction. But the tunnel-ram comes with a price. The initial outlay will be significantly greater as the intakes typically cost more, two carburetors must be used, and the necessary linkage must be obtained. Then there's the tuning effort needed to make the system work properly. Do not expect to bolt on a tunnel-ram, set the idle, and go. Considerable toil went into making all of the essential adjustments to the carburetion for the correct fuel metering particularly at high rpm where tuning is even more critical. Then there's the hood clearance issue. The tunnel-ram will more than likely not fit under any stock hood.

As far as the Indy manifold is concerned, we were surprised to find a four-barrel intake that came as close to the output of the tunnel-ram as this one did. Indy certainly did its homework when it produced this clean-slate design. For sheer user-friendliness, look no further than the Indy manifold. We bolted this induction on and laid down well over 500 hp at the wheels. It doesn't get any simpler. Hood clearance with anything more than a 1-inch filter element may be a problem, but the packaging is much more user-friendly than it was with the ram. Indy Cylinder Heads has produced a winner. Not only did it keep the tunnel-ram in sight, it proved much less complex to set up. With the Indy intake, you don't need an expert tuner to get you dialed in. Just bolt it on, make big power and go. For many, that's good enough.

Tunnel-Ram TrendsThe advent of big (large port volume) aftermarket cylinder heads for unlimited racing classes created the need for new-age tunnel-ram designs. How do the modern units differ from the rams of old? Glad you asked. Old-style rams were designed to run at rpm levels typical of the day with available production cylinder heads, which had port volumes a great deal smaller than many of today's aftermarket cylinder heads. The old rams were tall and had long runners that promoted low-end torque. The trend today is for shorter, fatter, tapered runners designed to promote high-rpm horsepower. Tunnel-ram manifold technology has evolved to address this high-rpm need, with vastly improved cylinder heads, cams, and lightweight valvetrains.
Dyno Results
Tunnel-Ram Single-Quad
RPM HP TQ HP TQ
4,000 279.5 365.2 279.7 364.5
4,500 339.2 393.8 328.1 379.3
5,000 410.2 429.5 397.9 413.9
5,200 423.6 429.7 414.7 420.2
5,300 431.1 428.1 429.3 424.3
5,500 444.7 424.4 434.6 414.6
6,000 485.7 422.4 468.7 408.9
6,500 505.8 409.2 491.8 397.0
7,000 529.3 396.1 513.0 383.4
7,100 531.5 392.6 512.6 380.0
7,300 525.0 376.4 463.9 333.9

The CombinationOur '68 Barracuda is packing a 340 between its framerails. Admittedly, a 13.6:1 test engine is on the extreme end of the "street" scale, but what better to test the limitations of an intake with than a high-rpm, high-compression power plant? The combo is as follows:*'69 340 ci plus 0.040 overbore (346 inches)*Arias forged pistons, 13.6:1 compression*Block half filled with Moroso Hard Block*Eagle I-beam connecting rods*Stock forged-steel crankshaft*Comp solid flat-tappet cam, 263/268 @ 0.050-inch valve lift, 0.640/0.640 after lash*Mopar Performance W-2 iron cylinder heads, ported, 2.02/1.60 valves*Crane 1.6:1 roller-rocker arms*Smith Brothers custom-length pushrods*TTI 171/48-inch headers with TTI 3-inch mandrel-bent exhaust system with Goerlich 3-inch welded mufflers *Mallory HyFire VI digital ignition*MSD billet mechanical-advance distributor*Milodon oil pump and pickup*Milodon 7-quart oil pan

Read more: http://www.carcraft.com/techarticles/cc ... z1kUNdv9xm


afr_235cc_intake_mini.jpg

heres some new 235cc AFR head ports just what a good tunnel ram intake and a good SOLID roller cam require on a killer sbc to max the air flow into the cylinders, just be aware that heads and a combo that will efficiently use the tunnel ram intake design will require a SOLID LIFTER cam with about .650 plus lift and duration in the 245-265 at .050 lift and tight 106-110 lsa range that matches,that intake flow, that will be designed to operate in the 4500-7800rpm PLUS ranges most of the time and normally a rather large 377-427 displacement and 10.5:1-13:1 compression and open tuned headers
 
A few links worth reading thru

http://www.superchevy.com/how-to/engines-drivetrain/sucp-0612-big-block-tunnel-ram-intake/
flowarea.jpg

and yes, your engines compression ratio,displacement,cam timing,exhaust headers and intake runner length, plenum volume and runner cross sectional area , ETC.all effect your results, but a properly tuned tunnel ram can make amazing power increases possible on some combos


http://www.superchevy.com/technical/eng ... ewall.html

http://www.carcraft.com/techarticles/03 ... _contrast/

http://www.profilerperformance.com/raci ... -tunnelram

By Richard Holdener
Super Chevy, December, 2006


When talk turns to tunnel ram intake manifolds, often times it seems they are placed in the same magical category as superchargers and individual-runner injection systems. These trick induction systems are bitchin' to look at and can be found on all manner of race hardware, which obviously means they have no place on a street motor, right?

While the streetability of a trick tunnel ram remains to be seen, we followed along on a comparison test that illustrated that at the very least a tunnel ram is much more than a simple high-rpm race manifold. Often placed in a different category than the more popular single and dual-plane intakes, the tunnel ram actually combines several beneficial design features of the two common intakes to produce what can be (on the right engine combination) the best induction system of the bunch. When you throw in the stunning visual effect of having a polished, dual-carb tunnel ram sticking out in the wind for all to see, the tunnel ram has a great deal to offer any performance big-block.

Intake manifolds for a typical V-8 like our 476 big-block Chevy test motor can be broken down into two basic categories, single plane and dual plane. A complete technical rundown would require more pages than we have available, but know that a dual-plane intake typically features long runners designed to promote low and mid-range torque production while keeping the power peak below 6000 rpm(in most cases).

Dual-plane intakes also effectively divide the V-8 engine into a pair of four cylinders by isolating the fuel and air supplied by the carburetor to each half of the engine. Isolating the two sides improves the signal to the carburetor. Combining the improved signal with the longer runners in the dual-plane, makes for an impressive street system. Dual-plane intakes are also available with the divider directly under the carburetor (used to split the motor) reduced or machined. This obviously does not transform the dual-plane intake into a single plane, but it does effectively shift the power curve (much like the installation of an open carb spacer).

Not surprisingly, single-plane intake manifolds differ from their dual-plane counterparts by way of a common plenum under the carburetor. Single-plane intakes typically offer shorter runners than the dual plane in inmost cases the design necessitates four shorter (inner) runners combined with four longer (outer) runners.

The use of a common plenum and shorter runners enhances high-rpm power. Unfortunately, the extra power production that occurs at the top of the rev range comes at the price of a reduction in power down low. Much like a wilder cam profile, the single plane manifold effectively shifts the torque production higher in the rev range (compared to a dual plane). Producing the same torque value at a higher engine speed will result in an increase in horsepower.

What this all means is that the choice between a single-plane and a dual-plane intake really comes down to the intended application. In most applications, the dual-plane design offers more low-speed power while the single-plane intake maximizes peak power production. For maximum street/strip acceleration (or maximum ultimate speed), the top-end power produced by the single-plane intake is usually the best choice. The dual-plane will provide the best overall torque curve, throttle response and fuel mileage.

Technically speaking, the tunnel ram manifold falls into the single-plane design category, as the tunnel ram shares the common plenum under the carburetor. The difference between the tunnel ram we used from Dart and the single-plane (Edlebrock 454R) was basically the runner length, plenum volume and use of an additional carburetor. The elevated position of the carburetor pad(s) on the tunnel ram allowed for longer and straighter runners, to say nothing of the fact that all eight of the runners were pretty much the same length (a trait not share by the single-plane intake).

The extended runner length helps to promote power production over a given rpm range. Basically speaking, the runner length (combined with cross section and taper) determines where the motor makes power. Naturally the intake runner length (and overall design) should be combined with the proper cam timing and cylinder head flow (and to a smaller extent header design) to optimize power production in a given range. Your choice of intake would certainly be different for a low-rpm towing engine for your dualie than for your 10-second Chevelle. The engine components (including the intake) should all be chosen to help reach a desired power curve to best suit the intended application.
bbtrm2.jpg

bbtrm1.jpg


Speaking of applications, to properly demonstrate the performance merits of the tunnel ram, we needed a cool big-block Chevy test motor. Rather than order a GM crate mill or screw together a rebuilt 454, we took Westech's Steve Brule up on an offer to use the race motor from his record-setting jet boat. The 476 was a serious piece, featuring 13.6:1 compression, CNC-ported heads from AFR and a serious sold roller camshaft. The 476 was basically a .100-over 454 that featured a Scat 4340 forged crank and matching rods combined with a set of JE pistons.

Breathing came from a set of 335cc (intake port volume) AFR aluminum heads. According to the flow bench, the heads flowed 410 cfm at .800 lift (not an unrealistic lift value given the wild cam timing). Comp supplied the hot roller cam (and the remainder of the valvetrain) that featured a .780/.744 lift split and a healthy 282/288 duration split (measured at .050). Additional components used in the build up included a Moroso oiling system (including marine pan and vacuum pump), a complete MSD ignition system (including crank trigger) and a set of 2.25-inch (primary size) Hooker headers.

As mentioned previously, an intake manifold should be chosen for a particular engine combination as well as the intended application. On this particular engine, the effective operating range was rather small, given the fact that the jet boat work much like a high stall converter. Once you hit the throttle to start the quarter-mile pass, the engines speed instantly climbs (up to around 6800 rpm) and the boat accelerates as the flow through the jet pump catches up with the engine speed. This means that the change in engine speed during the run is very minimal (500-800 rpm), and that every attempt should be made to maximize the power production in that rev range.

Having run the motor successfully with a combination of an Edelbrock Super Victor intake (with Dominator car flange) and a Barry Grant 1195 King Demon RS carb, Brule was looking to further improve the power output of his race motor. Given that it made peak power near 7400 rpm and the relatively narrow operating range, Steve decided the engine might be a good candidate for a tunnel ram. As he found out, not only was the tunnel ram impressive at elevated engine speeds, but it shined down low as well.

The first order of business was to establish a baseline with the Super Victor intake and 1195 Barry Grant King Demon carb. Equipped with the single four-barrel, the 476 produced 870 hp and 644 lbs-ft of torque. The power output was impressive considering the relatively small displacement. After successful back up runs produced the same power numbers, we replaced the Super Victor with the Dart tunnel ram and dual 1095 King Demon carbs. The longer runners in the Dart tunnel ram combined with the increased plenum volume and additional breathing offered by the pair of BG carbs to produce some impressive power gains.

Equipped with the Dart tunnel ram and dual King Demons, the 476 pumped out an even 900 horsepower and 670 lbs-ft of torque. Not only did the tunnel ram improve the peak power numbers, but the impressive induction system elevated to power and torque curves from 6000 rpm to 7400 rpm. Basically, the tunnel ram offered more power throughout the tested rev range. At these elevated specific output levels, it is difficult enough to even improve the power output, let alone show consistent gains throughout the rev range. The Dart tunnel ram was definitely the hot set up on this marine motor.

While this particular test was run on a dedicated race motor, we also ran another tunnel ram test on a much milder combination. The test mule was a low-compression 496-inch (.060-over and 4.25 stroker crank) big-block equipped with AFR 315 heads, a mild hydraulic roller cam (255/262 duration) and a set of Hooker Chevelle street headers. It was tested with a single-plane Holley 300-5 intake and a Weiand Hi-Ram (street/strip tunnel ram). The Holley intake was run with a 950 HP carb, while the Hi-Ram was run with a pair of tunnel-ram specific 750 cfm carbs.

Equipped with the single-plane Holley intake, the 496 produced 652 hp at 6300 rpm and 578 lbs-ft at 4800 rpm. After swapping on the Weiand Hi-Ram, the peak power numbers jumped to 687 hp and 618 lbs. ft. of torque. As with the 476 race motor, the tunnel ram improved the power output of the 496 stroker throughout the rev range (from 3000 rpm to 6500 rpm), further illustrating the impressive low-speed and mid-range power offered by the long-runner design.

Of course all the extra power comes with the cost of cutting a hole in your hood, but hood scoops are cool too, especially when they cover a trick (and effective) dual-carb tunnel ram.

Its always rather interesting to see the expression on some muscle car owners face when you diagnose a problem you find with a car engines tune, or when you locate an issue with a car like a restrictive exhaust, bad, ignition, or faulty timing or not having the fuel delivery system operating at peak efficiency, especially once youve corrected the problem and can demonstrate the improvement in performance.
it should be rather interesting to see the results, that you or anyone else would see, under similar conditions, if you locate some issue like a defective distributor or a fuel delivery issue or a vacuum leak for example.
If your engines not running correctly ,I would certainly not be shocked to find the older previous ignition was holding your engines power curve back, or not having the valves properly adjusted ,resulted in a good deal more power left on the table, than you might have imagined,
this of course is a very hard to diagnose issue unless you have lots of previous experience and are actually on-site to hear and feel the engine run,

I would suspect you, should reasonably expect too see,an improvement.
especially in the upper rpm ranges,
now that the ignition systems operating correctly.

if you re-tune the car now that the ignition is working correctly,
I'd strongly suspect you should easily see, a noticeable power increase in the 5000 rpm,
and up range.

most people don,t fully realize that just having the ignition advance curve,
a couple degrees off of the ideal, from the ideal, ignition advance curve,
the engine would best operate with,
could easily reduce the peak power you see by 40-70 hp or more.

(keep in mind theres several interdependent sub systems, and if any one of them is not optimum it effects all the sub systems potential, theres the fuel/air ratio,
the ignition advance curve,
( not just when the spark in relation too the crank and piston rotation,
but also the ignition voltage and amps, plug gaps and ignition wire resistance,)
the engine is going too be effected by, the cam timing, the valve train stability, the exhaust tune
(headers and low restriction exhaust behind the collectors)


GENERALLY your fuel/air ratio should be in these ranges
Idle- up too about
2500 rpm try for 14.7:1-15:1 f/a ratio,
too get max mileage and prevent spark plug fouling

from about
2500 rpm- too about 4500 rpm,
try to smoothly and predictably transition the fuel/air ratio mix richer to about 13.5:1
for good power and less chance of detonation

from about
4500 rpm- too about 6500 rpm and higher
,try to smoothly and predictably transition the fuel/air ratio mix richer to about
12.5:1,
for good peak power and less chance of detonation.

this is only a well proven starting point on the tune,
but it generally gets you in the ball park ,

and tends to reduce the chances of the engine reaching detonation conditions.
the ignition advance curve needs to be checked, the chart below is a very good starting point to work from, and USE OF A RICHER FUEL/AIR MIX, WILL AT TIMES BE REQUIRED IN THE OFF IDLE TO 3500 rpm range, but the idea here is to keep the lower rpm and lower stress operations running at efficient fuel/air ratios to reduce plug fouling and improve mileage as youll generally spend 90% of the cars operational life on the street at under 4500 rpm.

chart3e.jpg

set the plug gaps at about .045, make sure the valves are adjusted correctly, I,ve seen guys gain or loose a 10th of a second and 3 mph from simply changing the ignition advance curve and spark plug gap.

post your results and more questions
having the correct tools at hand and the experience to use them correctly always helps, and even with 50 plus years Of experience , you can,t accurately guess, you need too test and accurately record the results of each change you make and you can,t do that {BY EAR} you need to use precision tools
Stoich.gif

EXFLOWZ4.jpg

volumetric.gif


without testing you simply guessing
GET A FUEL PRESSURE GAUGE AND MEASURE DON,T GUESS
how can you possibly set up your fuel system unless you know the pressure and flow rates required and what currently exist's
vgauge.gif


image_6238.jpg

this is the most consistently accurate I.R temp gun I've used for testing[/img]
42545.jpg

http://www.testequipmentdepot.com/e...1100200223789&utm_content=All Extech Products
INFRARED TEMP GUN

having accurately dialed in the cam (degreed) and having marked TDC on the tab and damper is mandatory.
DSCF1026.jpg

timinglite4.jpg


http://garage.grumpysperformance.co...ying-your-real-advance-curve.4683/#post-12672
 
Last edited by a moderator:
heres some rather good pictures of a comparison between a couple wieand tunnel ram intake designs, the PRO-RAM, (RIGHT SIDE) that was designed originally as an individual runner intake that would mount a HOLLEY 4500 carburetor , but was later modified to add a plenum , and adapted to the smaller Holley carburetor bolt pattern mount size, when it was realized that the individual 4500 throttle bore diameter was restricting power potential, and the later wieand tunnel ram (LEFT SIDE) designed for the smaller 4160 type Holley carburetor s with a true plenum


BOTH INTAKES CAN HAVE IMPROVED FLOW WITH SOME PORTING WORK

trampic1.jpg

trampic2.jpg

trampic3.jpg

trampic4.jpg

NOTICE THE INTERNAL MOUNT BOLTS SECURING THE PLENUM TO THE BASE THAT OCCASIONALLY GOT LOOSE CAUSING MAJOR PROBLEMS AND THE OFF SET RUNNER ENTRANCE ON THE PRO-RAM

trampic5.jpg

trampic6.jpg

EARLIER PRO-RAM ABOVE, LATER HIGH RAM BELOW


trampic7.jpg

trampic8.jpg


efitu2.jpg

ABOVE AND BELOW YOU SEE WHERE THE TUNNEL RAM INTAKE WAS CONVERTED TO USE INJECTORS CONVERTING IT INTO MPFI
tunnelramefi1.jpg


hly-112-538_w.jpg

HLY-112-577.jpg

OBVIOUSLY THE PREVIOUS CARBURETORS WOULD BE REPLACED WITH A PAIR OF MATCHING THROTTLE BODYS, the advantage of course is direct port fuel injection and ore precise and even fuel distribution, and a more responsive engine once properly tuned

BUT A DEDICATED STACK EFI INJECTION manifold HAS ADVANTAGES in that stack length effectively changing the tuned rpm range are available
BBCCanteda.jpg


portedhsr.jpg

porting helps flow significantly, this is a SIMILAR SBC STEALTH RAM BASE BUT YOU CAN SEE SIMILAR MODS CAN BE DONE
 
tramp1.JPG

many tunnel ram intakes can be adapted, by a decent machine shop, to dual throttle bodys and injection, vs carb use
tramp9.JPG

a decent machinist can make custom runner extensions for most tunnel ram intake designs and for a limited few common designs they are available commercially already
tramp3.JPG

obviously you will need to carefully port match some intakes to some head ports due to the wide variation in sizes and shapes

tramp2.jpg

tramp4.jpg

shop carefully theres a big variation in both runner cross sectional areas and runner length and plenum volume, all effect the power range where they operate efficiently
tramp5.jpg

tramp6.jpg




tramp9.jpg

tramp8.jpg


tramp7v.jpg

tramp10.jpg
 
edl-70855c1.jpg

edl-70855b1.jpg

edl-70855a1.jpg

edl-3879_w.jpg

edelbrock recently came out with an improved tunnel ram designed to use throttle 4500 size bodys and injectors for the BBC rectangle port heads part #70855 for roughly $600 for the base
http://www.summitracing.com/parts/edl-70855
http://www.summitracing.com/parts/edl-7086 top plate $200
http://www.summitracing.com/parts/edl-3659 fuel rail kit $150
http://www.summitracing.com/parts/edl-7077 throttle linkage $140
http://www.summitracing.com/parts/edl-3879 DOMINATOR THROTTLE BODYS $500 EACH
youll still need a controller and sensors and a wire harness
65lb-85 lb injector sets should cost in the $400-450 range if you shop, and while that setup is not cheap its competitively priced
 
540Hotrod said:
I drilled the intake and *fit* the bungs to the intake...then took it to a little local welding shop to have them heliarced and add some braces for the fuel rails to bolt to. I don't have a heliarc welder. Worked out great.
tunbungs.png

JIM

Theres ALWAYS been and will likely always be a constantly expanding list of expensive shop tools most of us wish we could afford,use and learn to use with the skills to make most of the guys we sub out work too delirious,with envy, I don,t know about you but I hate to pay out cash for work to be done simply because I don,t own the tools to do it myself!
I'm also one of the guys that likes to see custom fabricated components that exactly match an application, that were carefully hand fitted and clearanced by someone who understands how and why the works correctly done! rather than a bunch of off the shelf parts that were just unpacked and bolted together.
but I don,t know anyone whose purchased a good TIG welder that regrets spending the cash. I went out and purchased a used tig decades ago, now Ill be the first guy to admit theres much better choices now, but at the time it seemed to be a valid choice.

I bought a ANCIENT 1980s TIG 330 amp welder used for a bit less than $1000 with a liquid cooled torch and accessories ,GAUGES , it may be old but it TIG welds just fine, and has paid for itself many time over in that length of time
330ampmiller.jpg


Id buy one of these TIGS now
http://www.htpweld.com/products/tig_welders/tig201.html
 
cant seem to find pricing on those tigs grumpy... but i imagine i would have to sell the vette to own one.
 
Ill get you current pricing monday, I'll call but the last couple guys I know who bought one said they were several hundred dollars less than a comparable miller or lincon TIG, and had a bit better features for the money.
Call us at 800-USA-WELD (800-872-9353) for more information or to place an order.
THE PREVIOUS 201 IS NOW DISCONTINUED
its been replaced with an upgraded 221 TIG $3520 THIS INCLUDES THE LIQUID COOLED TORCH AND TORCH'S COOLANT FLUID PUMP
http://www.usaweld.com/TIG-WELDER-Inver ... 12.5-3.htm
WATCH VIDEO s
https://www.youtube.com/watch?v=8i14t_CDMMQ

https://www.youtube.com/watch?v=JZMDAV87gn0

https://www.youtube.com/watch?v=w9Hm08GIBro

htptig.png


REMEMBER the LIQUID COOLED TORCH AND COOLANT PUMP PURCHASED SEPARATELY ,GENERALLY ADDS $1200-$1500 to a TIG WELDER and its a VERY GOOD OPTION TO HAVE


COMPARE TO MILLER 210 $3520 KEEP IN MIND THIS IS A AIR COOLED TIG < YOU WOULD NEED TO UPGRADE TO A WET TORCH AND COOLANT PUMPMaxstar 200 DX: Complete Pkg w/Foot Control (Water Cooled)
Maxstar 200 DX power source
Quick Reference Guide: English | Spanish
8 ft (2.4 m) primary cord
2-Wheel trolley cart (300480)
Coolmate™ 1 cooler 120 VAC (300360)
1 Gallon coolant (043810)
RFCS-14HD foot control (194744)
25 ft (7.6 m) Weldcraft® WP20 water cooled torch (300185)
Torch accessory kit with tungsten includes:
- Shielding cups
- Collets-1/16, 3/32, 1/8
- Collet bodies-1/16, 3/32, 1/8
- 2% Cerium tungsten-1/16, 3/32, 1/8
15 ft (4.6 m) Work lead with clamp and Dinse connector
Gas hose
Smith Regulator/flowmeter
Torch cable cover
Setup DVD $4,429.00

http://www.welders-direct.com/mm5/merch ... Code=m-tig

COMPARE TO LINCOLN 225 $2525 KEEP IN MIND THIS IS A AIR COOLED TIG < YOU WOULD NEED TO UPGRADE TO A WET TORCH AND COOLANT PUMP
http://www.welders-direct.com/mm5/merch ... Code=l-tig
 
very interesting... i think thats an invaluable skill... we talk about it here all the time but having the tools and the ability to use them, a good welder and a good mill go a long way towards making you unstoppable... with those kind of resources at your fingertips... impossible is nothing.
 
a video worth watching all the way through,
but keep in mind the results,
with the swap to a tunnel ram intake,
would have been noticeably better,
by boosting the compression to 11:1 -12:1
careful port and runner and combustion chamber clean up work,
un-shrouding the valves,
with a solid roller cam, with about
a 248-250/ 255-258 dur
.570-600/.580-610 lift on LSA 106-108 LSA
and obviously better flowing heads with a carefully matched set of long tube headers could further boost the power and torque band

especially if used with a cam designed to benefit stack injections flow characteristics
most BBC stack injection reacts well to a tight LSA like 106 and higher compression levels


LSAChart01.jpg

https://www.crower.com/camshafts/chevy-262-400-ultra-beast-roller-cam-285r.html

or
https://www.summitracing.com/parts/crn-118741
TUNNEL RAM INTAKES GENERALLY SHOW A NOTICEABLE IMPROVEMENT WITH A MATCHED TUNED HEADER CONFIG
pistonposition2a.jpg
volumetric.gif
anything you can do , to increase horse power with a tunnel ram,
can be duplicated and in most cases significantly improved with a stack injection set up.


BBC_Lucas_Timed_Injection-1024x897.jpg

exhaustpressure.jpg
EXFLOWZ4.jpg
 
Last edited:
BBC Tunnel Ram Triple Test
http://www.powerperformancenews.com/tech-articles/bbc-tunnel-ram-triple-test/

Not all BBC tunnel rams are created equal. The right intake can be worth as much as 78 extra horsepower.
Words And Photos: Richard Holdener

Is there anything better than a big-block powered Camaro, Chevelle, or El Camino? Heck, stick a big block in just about any vehicle and watch the instant transformation from mundane to maniacal. What could be better than a big-block powered classic (or modern) Chevy? How about a big block equipped with a dual-quad tunnel ram? Let’s face it, on the induction cool scale of one to 10, a tunnel ram rates a solid high nine. About the only thing that rates higher is a big, nasty roots blower poking out of your hood, but a bitchin’ dual-four barrel, tunnel ram is right there in terms of street presence.

I can remember seeing my first (working) tunnel ram back in high school. Like most t-rammed street motors, the small (283) Chevy surely didn’t need all the airflow (and fuel) supplied by the dual 660, center squirter Holleys, but that kind of logic really wasn’t the point. This particular early Nova had the right stance, courtesy of a set of air shocks, the right big rear/little front-tire combo and even the requisite set of traction bars. Was the 283-powered Nova the quickest car in the parking? Not by a long shot, as a host of other, considerably less extravagant machines could easily clean its bowtie clock, but not many drew as much attention on cruise night. Rolling down the boulevard, (okay, so it wasn’t exactly Woodward, but it was the main drag in our little town) with a pair of Holleys sticking out of the hood practically guaranteed a double take. What more could a Chevy enthusiast ask for?

Call me greedy, but even a high nine on the cool scale might not be quite enough when it comes time to choose performance parts, especially for my driver. One school of thought favors the notion that form follows function. The application of this logic with regards to the tunnel ram dictates that the only reason that a manifold should stick out of the hood is that it makes more power than one that doesn’t. Sounds reasonable, right? Of course this completely ignores the ability to actually watch the linkage open those eight butterflies as you roar off from the light—talk about way cool!

Still, wouldn’t it be nice to have a motor that actually takes advantage of the benefits offered by a tunnel ram or for that matter, to discover what those benefits might actually be? Taking things even further, how about discovering the power differences between different tunnel rams? One thing we discovered during testing of a trio of different tunnel rams on our 540 Dart SHP motor was that all manifolds are not created equal. Truth be told, like most induction systems, tunnel rams are actually designed for specific applications and rpm ranges.



The Dart 540 SHP short block consisted of a Dart Big M block stuffed with a forged steel 4.25-inch stroker crank, forged connecting rods and forged aluminum flat-top pistons. We added Fel Pro gaskets and ARP head studs to ensure the heads were properly secured.

The 8.8:1 compression short was equipped with a COMP solid roller cam featuring a .742/.715 lift split, a 271/280 duration split (@.050) and a 112-degreee lobe separation angle. The cam also featured a 4/7 firing order swap.

What better heads could there be to top off the SHP short block than Dart’s own Pro 1 CNC BBC heads? According to Dart, the Dart Pro 1 345 heads flowed just under 400 cfm at .800 lift.
A great deal of confusion exists about tunnel ram manifolds, the first of which is that all tunnel rams are basically race-only manifolds. Actually, there are a great many different tunnel ram manifolds available (at least for Chevy applications) that offer decidedly different power curves. Like any intake manifold, the power produced by a tunnel ram is decided primarily by the runner length. Sure, the plenum and runner volume affect power production, but the real key is the runner length. A number of tunnel ram intakes, like ours from Weiand, Dart and Wilson Manifolds actually offer longer runner length than a typical single-plane intake. The tunnel ram combines the common plenum of the single plane with the long runners typically offered in a dual-plane intake–kind of the best of both worlds. The other benefit to the tunnel ram design is that it offers near-identical runner length for each cylinder.

Take a look at a typical single (or even dual) plane intake and check out the difference in runner length for each port. This difference in runner length optimizes power production at different rpm ranges in each cylinder (based on cylinder filling). The tunnel ram offers improved power over a typical single-plane intake by having all the cylinders produce the same effective power curve. In our testing we even added porting to the mix in the form of an as-cast Dart tunnel ram massaged by the flow experts at Wilson Manifolds. Would our low-compression, 540 big block respond to the improvements made by porting the Dart tunnel ram? Only the dyno would tell.


The first tunnel ram tested on the BBC was a Weiand Hi-Ram. The Weiand tunnel ram was designed to accept a pair of 4150 Holley carburetors.

The Weiand tunnel ram was run on the 540 BBC with a pair of 950 HP Holley carburetors.
With the cool factor and design theories established, the only thing left to do was get them on the dyno. Our trio of manifolds included a Weiand Hi-Ram tunnel ram, a Dart as-cast tunnel ram, and a second Dart tunnel ram massaged by Wilson Manifolds. According to literature supplied by Holley (Weiand), the Hi-Ram was designed for use on a performance big-block Chevy with an effective operating range of 2800 to 8,000 rpm. Of course we had no intention of running our big block anywhere near 8,000 rpm, but our calculations indicated that the runner length of the Hi-Ram would allow a power peak past 6,500 rpm on our test motor.

Holley shipped the Hi-Ram with a pair of 950 HP carburetors. Some enthusiasts might see a pair of 950 carbs as a tad overkill on the big block, but the pair of HP-series Holley’s worked perfectly on our 540. If anything, the aggressive cam timing had more of an effect on low-speed power and drivability than the use of dual quads. Properly tuned, tunnel rams offer an impressive combination of power and drivability thanks to their all-important average power production.


All testing was performed on the engine dyno using a set of 2.25-inch Hooker headers feeding 18-inch collector extensions.

Ignition chores were handled by MSD including a crank trigger to ensure accurate timing.

Having previously run all manner of combinations on the Dart SHP 540, including nitrous and pair of superchargers, the big block was definitely ready for synthetic oil. All testing was run using Lucas 5W-30 synthetic oil.

Equipped with the Weiand tunnel ram and dual 950 HP carburetors, the 540 BBC produced 777 hp at 6,600 rpm and 681 lbs/ft of torque at 5,600 rpm. This represented a significant jump in power over the single-plane intake and single Dominator carb, which produced 770 hp and 663 lbs/ft of torque.
While there is no denying the visual appeal of a tunnel ram, you shouldn’t just go hog wild and pop one on your stock 396 and call it good. Well, you could (and it would look cool), but it wouldn’t work as well as if you built a motor capable of using the performance offered by the unique design. To that end, we resisted the temptation to install one on an otherwise stock 396 motor or, for that matter, a 454 crate motor. Instead, we assembled a suitable test mule capable of the kind of power and rpm suitable for our tunnel ram test. Rather than run a smaller 454 or even 496 stroker, we selected a big block sporting 540 cubic inches.

The Dart SHP short block was equipped with a bevy of forged internals including a 4.25-inch stroker crank, rods, and forged flat-top pistons. The SHP 540 was topped off with a set of CNC-ported, Dart Pro 1 heads, and a healthy COMP roller cam offering .742/.715 lift split, a 271/280 duration split (@.050) and a 112-degreee lobe separation angle. The combination also featured a Moroso oiling system including a billet oil pump, pick up, and oil pan with integrated windage tray. We also employed an MSD crank-trigger ignition system, Hooker headers and Ultra Pro Magnum roller rockers.

Prior to running our trio of tunnel rams, we established a baseline by running a single four-barrel, single-plane intake. The Weiand Team G was designed to accept a 4500 Dominator carb. After jetting and timing, the 540 produced 770 hp and 663 lbs/ft of torque. Torque production with the single plane exceeded 600 lbs/ft from 4,200 rpm to 6,700 rpm. Next up was the first of the tunnel rams, the Weiand Hi-Ram and pair of 950 HP Holleys. Once again jetting and timing were optimized, though the 950 HP Holleys were very close right out of the box.

The Weiand tunnel ram improved the peak power numbers to 777 hp at 6,600 rpm and 681 lbs/ft at 5,600 rpm. Though a peak gain of just seven horsepower doesn’t sound like much, the differences were much more significant elsewhere in the rpm range. Measured peak to peak, the Weiand tunnel ram offered nearly 20 additional lbs/ft of torque, but the difference was more than 30 lbs. ft from 4,500 rpm to 5,000 rpm. In fact, the Weiand tunnel ram offered more power from 3,500 rpm to 6,800 rpm, something that can’t be attributed to running an extra carburetor. Credit the long runners in the tunnel ram for the additional low and mid-range power (up to 6,800 rpm) over the single plane, but also note that the shorter runners in the single plane offered slightly better power at 7,000 rpm.


Next up was the Dart tunnel ram. According to Dart, their dual-quad intake was designed to offer the performance of a custom sheet-metal intake for the price of a casting. Different tops were available for the Dart tunnel ram, but we stepped right up to the lid designed to accept a pair of Holley Dominators.

To properly feed our Dart tunnel ram, we chose a pair of new Ultra Dominator carbs from Holley. The new Ultra-series Dominators offered a number of desirable features, including lightweight, aluminum construction, hand-polished venturi inlets and billet metering blocks.

One of the many features that set the Ultra Dominators apart from their standard counterparts was externally adjustable linkage.

Equipped with the Dart tunnel ram, the 540 BBC produced peak numbers of 806 hp at 6,700 rpm and 694 lbs/ft of torque at 5,500 rpm. Up at 7,000 rpm, the Dart tunnel ram was worth 51 hp over the Weiand tunnel ram.

lg.php

Having run this test previously on our 540, we expected the Weiand Hi-Ram to shine compared to the single-plane, Team G intake, but how would it now compare to another tunnel ram? To illustrate the differences, we replaced the Weiand Hi-Ram with a Dart tunnel ram. According to Dart literature, their tunnel ram was designed to combine the performance of a custom-built, sheet-metal intake for the price of a cast manifold! The tunnel ram featured curved runners designed to meet the cylinder head ports at the proper angle to reduce turbulence during the transition.


The runners in the tunnel ram were also tapered to maximize intake charge velocity for more complete cylinder filling. Interchangeable top plates are available for both inline and sideways carburetors mounting as well as electronic fuel injection (with the fuel injector housing cast directly into the manifold). Both tall and short-deck manifolds are available and designed to use standard length distributor (small cap required). For our 540 BBC, we chose a top designed to accept a pair of 4500 Holley Dominator carbs.

To feed our new tunnel ram, we installed a pair of Holley 1050 Ultra Dominators. The Ultra-series Dominators featured many improvements over the already-impressive standard Dominators, including aluminum bodies, billet metering blocks and fully adjustable, external linkage. The trick Ultra Dominators also featured high-signal, billet booster inserts, a tumble-polished finish on the main body and fuel bowls and even hand-polished venture inlets to maximize airflow. Naturally the Dominators also featured adjustable idle feed, emulsion, and power valve restrictors in the metering blocks for near-infinite tunability.

Run with the Dart tunnel ram and Ultra Dominator carburetors, the 540 BBC produced peak numbers of 806 hp at 6,700 rpm and 694 lbs/ft at 5,500 rpm. Measured peak to peak, the Dart tunnel ram improved the power output by 29 hp and 13 lbs/ft of torque, but the gains were as high as 51 hp at 7,000 rpm. Given the big gains at the top of the rev range, it would seem the Dart tunnel ram was tuned for top-end power, but such was not the case. The 540 produced more power with the Dart tunnel ram even down at 4,000 rpm, though the Weiand offered more power in a narrow range from 4,600 rpm to 5,100 rpm.


After running the Dart tunnel ram, we couldn’t help but wonder if there was any more power to be had through porting. To illustrate the possibilities, we shipped one of the Dart tunnel rams over to the flow experts at Wilson Manifolds.

To say that the porting was a work of art is an understatement. Even more impressive was what you couldn’t see, including a dramatic change in the taper ratio of each port.

Naturally the intake was port-matched to the Dart Pro 1 heads to eliminate any flow disruptions that occur during the transition from the manifold to the head port.
The final test was to run the Dart tunnel ram supplied by Wilson Manifolds. Wanting to test the power potential offered by porting, we sent a second Dart tunnel ram to the flow gurus at Wilson Manifolds. They cut, welded and ported the daylights out of the tunnel ram, but the finished product was something you’d be proud to show your friends. In fact, we hated having to hide the precision porting with the carburetor lid. Critical changes to the as-cast manifold included alterations to the taper ratio, port entries and transition between intake and cylinder head. Basically they took the casting and improved it everywhere, without any major external alterations, save for an aluminum badge proudly displaying Wilson Manifolds and the attending serial number.

While a street racer might not want to advertise, what Chevy enthusiast wouldn’t be proud to display the fact that their big block was sporting something more than an as-cast tunnel ram? Impressive visually, the Wilson-ported manifold performed even better, as the massaged tunnel ram improved the power output of the 540 to 833 hp at 6,800 rpm and 712 lbs/ft at 5,600 rpm. More than just peak power gains, the Wilson porting improved the power output right from the get go (nine lbs/ft at 3700 rpm), though the major gains (as high 27 hp over the as-cast tunnel ram) came higher in the rev range. Compared to the Weiand tunnel ram, the Wilson-ported Dart intake improved power production by as much as 78 hp, though it should be said that this extra power will cost significantly more than the as-cast Weiand intake.


After installing the Wilson-ported Dart tunnel ram, we installed the pair of Holley Ultra Dominator carbs.

I guess the guys at Wilson Manifolds really know what they are doing, as the ported manifold increased the power output of the 540 BBC from 806 hp and 694 lbs/ft to an impressive 833 hp at 6,800 rpm and 712 lbs/ft at 5,600 rpm.

bbcttt1.png

bbcttt2.png
 
Last edited:
Back
Top